In order to improve performance of various safety apparatuses such as a seat belt and an air bag, for example, mounted at a vehicle, operations of such safety apparatuses may be controlled on a basis of a weight of an occupant seated in a seat. JP2009-128106A, which is hereinafter referred to as Patent document 1, discloses a strain sensor known as a load detection apparatus detecting a weight of an occupant seated in a seat for a vehicle. The strain sensor disclosed in Patent document 1 includes a strain element, two fixation support members holding the strain element by fitting in two fixation holes provided at the strain element, and a bracket member including connection holes which secure the fixation support members. One of the two connection holes of the bracket serves as an elongated bore elongated in a direction where the connection holes are disposed side by side.
According to the aforementioned construction, a variation in manufacturing dimensions of the two connection holes of the bracket member is compensated by the configuration of one of the connection holes, i.e., the elongated bore. Thus, without a highly accurate manufacturing of the bracket member, the bracket member may conform to an attachment dimension between a pair of fixation shafts to which the fixation support members are inserted to be positioned. As a result, the bracket member with a high manufacturing accuracy is not required, which may lead to the load detection apparatus at a reduced cost.
According to the strain sensor disclosed in Patent document 1, fixation holes provided at opposed end portions of the strain element are fitted to the fixation shafts of a floor fixation member. Thus, an attachment position of the strain sensor needs to conform to a distance between the fixation shafts. At this time, because the distance between the fixation shafts differ and vary depending on a seat configuration, the strain element, for example, needs to be newly provided each time the distance between the fixation shafts is changed. The strain element is a member which most influences a sensor output accuracy. Thus, a usage of a highly accurate manufacturing process of the strain element may lead to a manufacturing cost thereof greater than other components. In order to avoid a cost for newly providing the strain element each time the distance between the fixation shafts is changed, it may be considered to decrease the accuracy of the manufacturing process of the strain element. Nevertheless, the sensor output accuracy is affected so that the sensor accuracy may decrease.
A need thus exists for a load detection apparatus which is not susceptible to the drawback mentioned above.